This invention relates to printing processes involving lenticular lens material and, more particularly, to such a printing process in which a thin sheet lenticular lens material is used and in which high quality printing, with desired optical effects, is achieved.
Lenticular lenses are known and used in the printing industry primarily in the printing of advertising and promotional materials, packaging labels, hang tags for merchandise, product tags, and security labels. A preliminary step in a printing process includes selecting segments from two or more visual images used to create a desired visual effect and interlacing these segments. The interlaced segments are then mapped to a selected lenticular lens material in a prepress operation, so when the segments are printed on the material the final result exhibits a desired visual effect such as zoom-in, zoom-out, stereoscopic or 3-dimensional, and movement. The lenticular lens material used in this printing process includes a transparent web which is flat on one side with a plurality of lenticules being formed on the other side. The mapped images are printed directly onto the flat side of the lens material. The lenticules comprise convex lenses formed in a side-by-side arrangement with the lenticules extending parallel to each other the length of the web. Different lens materials have a different number of lenticules per inch (LPI) with the particular LPI selected depending upon the particular application. Once the image segments and material is selected, the previously noted prepress operation is performed with the image segments being mapped with respect to the focal points of the lenticules on the selected lens material.
The major cost component in a lenticular printing operation is the lens material. Heretofore, the lens material has typically been between 20-25 mils thick and the material cost has represented 50-75% of the total cost of a printing project. It is therefor beneficial to try to reduce the cost of the lenticular lens material, if this can be done without sacrificing the quality of the printed product. One way of reducing cost is to decrease the thickness of the lens material. However, doing so creates significant problems which must be overcome to produce a quality product. For example, even though sheet thickness is reduced, the LPI of the material is actually increased. This means that the width of each lenticule is narrower which, in turn, reduces the margin of error which is acceptable during printing. Factors such as temperature, humidity, uniformity of pressure exerted on the material as it is drawn through the printing press, all also have a greater impact on the quality of the printed material than with a conventional thicker lens material. Non-uniform pressure will cause a thin lens material to stretch, distorting the material and causing the printed pattern to no longer be aligned with the focal points of the individual lenses. Similarly, if the temperature and humidity to which the lens material is subjected is not maintained at a constant value, the material will again distort with an unacceptable result being produced.
Overall, and in accordance with the present invention, the quality of the printing operation has been found to be best controlled by meticulously controlling the alignment of the film, printing plates, and lens material prior to the start of printing. In addition, by controlling the pressure on the material as it is run through the press, the temperature and humidity in the area where the press is located, distortions which may occur during printing are further minimized or eliminated altogether. The printing process of the present invention overcome the numerous problems which must be addressed during press set-up and the subsequent printing operation so the result is a printed sheet of lenticular lens material which has the clarity and color delineation required to produce the visual effects desired by the customer.
Among the several objects of the present invention may be noted the provision of a lenticular printing process employing a lenticular lens material substantially thinner than conventional lens materials, but which provides superior visual qualities for materials printed using the lens. In particular, the optical effects produced using the thin lens material with the process of the present invention are comparable to, if not significantly better than, those achievable using lenticular lens material of a conventional thickness, but achievable at substantially less cost.
Another object of the invention is a printing process in which alignment and registration of the colors to be printed are done not only to each other prior to printing, but also to the lens material. That is, during press set-up, the film negative for each of the four process colors (black, cyan, magenta, and yellow) are registered to one another; and in addition, to the focal points of the lenticules in the lens material. By proper alignment and registration of the negatives to each other and the lens material, total deviation from perfect registration can be controlled to less than one-half of one lenticule; this despite the fact that the width of the lenticules are substantially less than that of lenticules on conventional lens materials.
Another object of the invention is a printing method in which perfect squareness of the film to the printing plates and printing plates to the lens material is achieved. That is, the film is first stripped so the negatives are perfectly square or in registry with each other. The printing plates are next adjusted and mounted to be perfect square. Finally, the lens material is set-up to be and is maintained perfectly square through the printing process. Apparatus used in the set-up portion of the process is provided to achieve an exacting level of alignment and dot pattern registration throughout the printing process.
A still further object of the invention is a printing process by which substantially more phases (interlaced segments subtended by a lenticule) are accommodated than has previously been possible. Up to fifty percent more phases are acceptable with the thin lens material used in the process despite the fact the material is only between one-half and three-quarters the thickness of conventional materials and has substantially more lenticules per inch.
Yet another object of the invention is a printing process usable with different types of printing processes such as flexographic and lithographic printing, to produce an acceptable lenticular product regardless of the process employed. Regardless of the type of press used, the process of the present invention, and the associated apparatus, reduces the cost of a printing job by insuring that precision alignment and color registration is made between the film, plate and lens material prior to the start of a printing operation. This reduces the amount of film otherwise wasted during set-up as well as the run time for the job. Further, by acclimatizing the film to the press both before and during a run, effects of temperature, humidity, and pressure are also minimized. By using the lenticular lens material in the order in which it was produced, effects caused by any variations from one portion of a lot to the next are also minimized.
Finally, it is an object of the present invention to provide a printed product in which all segments of respective interlaced images are sharp and clear and in which desired visual effects incorporated into the final product are readily observed.
In accordance with the invention, generally stated, a lenticular lens material used in a printing process comprises a web of transparent material of a predetermined thickness, this thickness being between one-half and three quarters the thickness of conventional lenticular lens materials. In a prepress operation, interlaced image segments which produce a desired visual effect in a final printed product are mapped to the selected lens material. As an initial step in the printing process the film negatives are aligned with each other and the focal points of the lenticules on the lens material so the color dot patterns which are to be printed on the lens material properly register with each other. This is done both for the film negatives for each image color, and the printing plates made from the negatives. The negatives, plates, and lens material are adjusted, as necessary, at each stage prior to an actual print run. A special grid is used with the negatives and the plates installed on the press for this purpose, and registration control marks (combs) printed on the material by each color plate are used for final adjustment. Prior to beginning of a printing process, the lens material is acclimatized to the press to insure that the temperature level of sheets of lenticular lens material run through the press have a temperature corresponding to that of the impression and transfer cylinders used in the press. During printing, the selected lens material is run in lot, cylinder ID, and skid number sequence. The meticulous prerun set-up and environmental control of the press and its surrounding area results in a consistent registration of the dots printed on a flat side of the lens material to the lenticules formed on the opposite side thereof, so to produce a printed lenticular product with desired visual effects of a superior clarity. Other objects and features will be in part apparent and in part pointed and hereinafter.